The accepted methods of constructing concrete structures designed with a plurality of tiered or stepped levels, such as seating for lecture halls, theaters or stadiums or stairways, is usually determined by the size of the project. Structures, like sports stadiums, are large enough in size to benefit from the ability of using large customized concrete ‘gang type’ forms that require external means of load transfer from one section of the form to another. Forming smaller structures, like a classroom lecture hall, will often typically be built ‘by hand’ one component at a time.
The use of ‘gang type’ forms to build the larger structures can usually provide greater control over dimensional accuracy and installed costs due to a faster cycle of setting the forms, placing the concrete and stripping the forms. Employing ‘hand built’ construction practices for smaller structures can provide dimensional accuracy but there is increased risk of failure due to the reduced size of the components and fasteners, though the construction cycle will be longer and the labor cost will be higher. The decision ultimately comes down to whether there is enough labor savings to offset the investment in the ‘gang type’ forms. If the reuse and the labor savings can't be realized with ‘gang type’ forming methods, then ‘hand built’ forms are used for the construction, with the acceptance of higher labor costs and associated risks.
It is known in the industry to utilize expanded polystyrene (EPS) foam blocks as a form that supports the tread portion of a tiered concrete floor, for example, for the seating area of a cinematic movie theater. This prior art method does not form a concrete riser, such that the structure does not have the integrity of a monolithic tiered concrete slab having interconnected concrete risers and treads. Typically, this prior art method utilizes a permanent steel plate as the riser. In the event of a fire, the steel plate transfers heat to the underlying foam blocks, which then can melt such that the concrete treads are not evenly supported and eventually fail.
Another prior art method of forming a tired concrete slab requires a base with compacted granular fill which must be retained in a sloped arrangement. Retaining walls are used for retention of the sloped fill material. The retaining walls add additional time and expense to these projects.
Therefore, it is a primary objective of the present invention to provide an improved assembly and method for forming a monolithic tiered concrete slab or stairway.
Another objective of the present invention is the provision of an assembly and method for forming a tiered concrete slab or stairway having a curved riser face.
Another objective of the present invention is the provision of an assembly and method for forming a monolithic tiered concrete slab or stairway for various uses, including auditorium and lecture hall seating.
Another objective of the present invention is the provision of an assembly and method for forming a tiered concrete slab or stairway having minimal heat transfer properties.
Still another objective of the present invention is the provision of an assembly and method for forming a tiered concrete slab or stairway having interconnected concrete treads and risers.
Yet another objective of the present invention is the provision of an assembly and method for forming a tiered concrete slab or stairway which is customized to each individual project.
A further objective of the present invention is the provision of an assembly and method for forming a tiered concrete slab or stairway which is easy to use.
Still another objective of the present invention is the provision of an assembly and method for forming a tiered concrete slab or stairway which is economical and durable.
These and other objectives will become apparent from the following description of the invention.